The structure of a rolling piston type rotary compressor widely used in the compressor for an air conditioner is known as represented by a longitudinal sectional view in FIG. 8 and lateral sectional view of compression element in FIG. 9. In FIG. 8 and FIG. 9, the compressor comprises a motor 102 accommodated in an enclosed container 101, and a compression unit 103 driven by this motor 102. A drive shaft 106 of the compression unit 103 is coupled to the motor 102, and is supported by a main bearing 108 and a subsidiary bearing 109 disposed at both sides of a cylinder block 111. The motor 102 includes a stator 104, a rotor 105, and the drive shaft 106. Inside of the cylinder block 111 incorporating a cylinder 119, a roller 110 externally fitted to a crank unit 107 eccentric from the main shaft of the drive shaft 106 is disposed closely to the inner wall of the cylinder 119. Thus, a compression chamber 115 is formed. In a guide groove 112 of the cylinder block 111, a blade 114 and a spring device 113 for thrusting the leading end of the blade 114 to the roller 110 are disposed, and the compression chamber 115 is divided into the suction side and compression side. In the cylinder block 111, on the boundary of the blade 114, a suction port 116 opening to the cylinder 119 and a discharge port 117 are provided. An accumulator 160 for accumulating the low pressure side refrigerant is connected to the suction port 116.
In the rotary compressor in such constitution having one compression chamber 115, since compression torque fluctuations are significant, vibrations are large and the compressor piping system may be broken.
To solve such a problem, as shown in FIG. 10, a rolling piston type rotary compressor having two compression chambers in a cylinder 219 has been proposed. In FIG. 10, a first blade 221 and a first spring device 222 are disposed in a first guide groove 220 provided in a cylinder block 211, and a second blade 224 and a second spring device 225 are disposed in a second guide groove 223. Thus, a first compression chamber 226 and a second compression chamber 227 are provided. In the first compression chamber 226, a first suction port 228 and a first discharge port 229 are opened, and in the second compression chamber 227, a second suction port 230 and a second discharge port 231 are opened.
In the compressor in such constitution having two blades, the relation between the shaft rotating angle and required torque is shown in FIG. 11. As shown in FIG. 11, the compression torque action range per revolution of a drive shaft 206 is divided into two sections, and the compressor vibrations are reduced to half as compared with the compressor shown in FIG. 8. This constitution is disclosed in Japanese Laid-open Patent No. 63-208688.
On the other hand, the compressor having the first suction port 228 and second suction port 230 in the cylinder block 211 is constituted, for example, as shown in FIG. 12, in which a first accumulator 218 and a second accumulator 214 are disposed at the suction side.
To simplify the suction piping system, a constitution as shown in FIG. 13 is proposed in Japanese Laid-open Patent No. 1-249977. In FIG. 13, an accumulator 350 penetrates through a side wall of an enclosed container 301, and is connected to a suction port 349a of a first compression chamber. To a suction port 349b of a second compression chamber, the suction port 349a is communicating through a communication pipe 363 in the enclosed container 301. The passage entering the second compression chamber is communicating with the second compression chamber by detour. The communication pipe 363 is composed by evading the bearing boss of a main bearing 334 for supporting a drive shaft 336. That is, the length of the passage entering the second compression chamber has a path longer than the length of the passage entering the first chamber. Furthermore, the gas leaving the accumulator 350 is divided into two paths to get into the first compression chamber and second compression chamber respectively. In this case, the two divided flows of the gas are not uniform. In such conventional constitution, as mentioned below, there was a first problem relating to the flow of suction gas.
The principle of compression of the compressor forming two compression chambers in the cylinder by disposing two blades in one cylinder block is as shown in FIG. 6. That is, the shaded area in FIG. 6 (a) shows the state of maximum suction stroke volume in the compression chamber. The shaded area in FIG. 6 (b) shows the compression chamber immediately before closure of the suction port in the state of minimum suction stroke volume in the compression chamber, which is reduced from the state of the maximum suction stroke volume in FIG. 6 (a). This decrease in the suction stroke volume means that the suction gas flows back to the suction piping system through the suction port. The shaded area in FIG. 6 (c) shows the state of substantial start of compression after closure of the suction port. The shaded area in FIG. 6 (d) shows the state of discharge from the compression chamber through suction port and suction valve as a result of elevation of compression chamber pressure. Thus, flow-in and counter-flow of suction gas occur in the suction and compression strokes. Accordingly, the suction route is unevenly divided into two flows as shown in FIG. 13, and the path lengths of two divided flows are different, and in such constitution, therefore, pulsations occurring in the suction passage interfere with each other, thereby resulting in increase of suction passage resistance and significant drop of compression efficiency.
There was also a second problem. FIG. 7 shows a pressure state in each cylinder at each compression stroke. In FIG. 7 (a), the pressure in the cylinder opposite to the second plate 224 is low on both sides, and the pressure in the cylinder opposite to the first blade 221 is low on one side, and high on the other. Therefore, the roller side leading end of the second blade 224 and the roller 210 contact with each other by both thrusting forces, that is, the thrusting force of the second spring device 225 acting on the second blade 224 and the thrusting force by the differential pressure of the discharge pressure and suction pressure.
On the other hand, the roller side leading end of the first blade 221 and the roller 210 contact with each other by the combined thrusting force of the thrusting force of the first spring device 222 acting on the first blade 221, and the differential thrusting force of the thrusting force by refrigerant gas pressure distribution from the cylinder inside acting on the roller side leading end of the first blade (the thrusting force on the basis of the distribution rate of the compression intermediate pressure and the distribution rate of the suction pressure) and the thrusting force by discharge pressure. The contacting force of the first blade 221 and roller 210 and the contacting force of the blade 1141 and roller 110 in FIG. 9 are equal to each other.
In FIG. 7 (b), the pressure in the cylinder opposite to the first blade 221 and second blade 224 is low (suction pressure) on both sides. Therefore, the first blade 221 and the roller 210 of the roller side leading end of the second blade 224 contact with each other by receiving the same thrusting force as the second blade 224 in FIG. 7 (a).
In FIG. 7 (c), the pressure in the cylinder opposite to the first blade 221 is low on both sides, and the pressure in the cylinder opposite to the second blade 224 is low on one side and high on the other. Therefore, the roller side leading end of the first blade 221 and the roller 210 contact with each other by receiving the same thrusting force as the blade 224 in FIG. 7 (a). The second blade 224 contacts with the roller 210 by receiving the same thrusting force as the first blade 221 in FIG. 7 (a).
In FIG. 7 (d), moreover, the pressure in the cylinder opposite to the first blade 221 and second blade 224 is low (suction pressure) on both sides. Therefore, the first blade 221 and the roller 210 at the roller side leading end of the second blade 224 contact with each other by receiving the same thrusting force as the second blade 224 in FIG. 7 (a).
That is, from FIG. 7 (d) to FIG. 7 (a) and FIG. 7 (b), in other words, until the crank 207 rotates 180 degrees, the roller side leading end of the second blade 224 and the roller 210 contact with each other by the two thrusting forces, that is, the thrusting force of the second spring device 225 acting on the second blade 224, and the thrusting force by the differential pressure of discharge pressure and suction pressure.
On the other hand, from FIG. 7 (b) to FIG. 7 (c) and FIG. 7 (d), in order words, until the crank 207 rotates 180 degrees, the roller side leading end of the first blade 221 and the roller 210 contact with each other by the both thrusting forces, that is, the thrusting force of the first spring device 222 acting on the first blade 221 and the thrusting force by the differential pressure of discharge pressure and suction pressure.
As a result, the first blade 221 and the roller side leading end of the second blade 224 is greater in the contacting force than between the blade 114 and roller 210 in FIG. 7, and the wear occurs earlier than in the rolling piston type rotary compressor of the prior art. As a result, the durability of the first blade 221, second blade 224 and roller 210 is lowered.